RU2290453C2 - Method of forming multi-component stoichiometric film coat - Google Patents

Abstract

FIELD: application of thin films; forming multi-component stoichiometric film coats; electronic, atomic and other industries.

SUBSTANCE: proposed method consists in presetting some technological parameters: current intensity of magnetron discharge current, areas of target erosion zones and target density whose dependence is determined by properties of materials and stoichiometric coefficients or percentage of film material components at the following ratio:

, where ρ_i is density of target material of i-element; I_i is current intensity of discharge of i-magnetron; S_i is area of erosion zone of i-target; a_i is stoichiometric coefficient of i- element in chemical formula or percentage of i-element in film; M_ai is atomic mass of gas ions; E_ci is sublimation energy of is atoms of target of i-element; α_i is dimensionless parameter of material of target of i-element depending on Ma/Mu; ρ₁ is density of target material of base element having minimum density of compact material; S₁ is area of erosion zone of base element having minimum density of compact material; a₁ is stoichiometric coefficient of base element having minimum density of compact material of chemical formula or percentage of base element having minimum density of compact material in film; M_a1 is atomic mass of target material of base element having minimum density of compact material; E_c1 is sublimation energy of target atoms of base element having minimum density of compact material; α₁ is dimensionless parameter of base element target material having minimum density of compact material depending on M_a/M_u. Then, magnetron spraying of opposite targets is performed and sprayed material is directed to mixing zone by at least two counter flows of sprayed material. Each counter flow is directed away from substrate for forming resultant flow. Substrate is shifted relative to resultant flow and sprayed material is settled on substrate.

EFFECT: enhanced efficiency.

2 dwg, 4 tbl, 2 ex

Description

The invention relates to the technology of thin films and can be used in the formation of stoichiometric multicomponent film coatings for electronic, atomic and other fields of science and technology.

Known methods in which the formation of a multicomponent film coating is carried out by spraying ceramic or alloy targets [1]. Since complex chemical compounds are sprayed, it is not possible to control the concentration of their constituent components during the film deposition process, as a result of which the composition of the film coating formed in this way differs from stoichiometric.

The closest technical solution is the method of forming a multicomponent film coating [2], which consists in the fact that they perform magnetron sputtering of opposite targets, direct the sprayed material into the mixing zone formed by at least two opposing streams of sprayed material, and deviate the direction of each of the opposing streams of sprayed material towards the substrate with the possibility of the formation of the resulting stream of atomized material from the mixing zone to the substrate, which is moved relative to the resulting stream, and the atomized material is deposited on the substrate.

The disadvantage of this method is that when spraying opposing targets of heterogeneous components do not take into account the dependence of the concentration of the element in the mixing zone and in the film on the speed of its spraying. The sputtering rate in turn depends on the density of the ion current, the density of the target material, its atomic mass and sublimation energy, and the density of the ion current on the strength of the magnetron discharge current and the area of the erosion zone of the target. Therefore, if we spray opposite targets of the prototype, not taking into account the dependence of the stoichiometry of the formed multicomponent film coating on the strengths of the magnetron discharge currents, the areas of the erosion zones of the targets, the densities of the materials of the targets and the atomic masses of the materials of the targets, then the process of forming a multicomponent film coating will not provide the specified stoichiometric composition of the film.

The technical result of the invention is to improve the quality of coatings, their stoichiometry by properly setting the set of structural and technological parameters of the process of forming a multicomponent film coating, depending on the properties of the materials and stoichiometric coefficients of the chemical formula or the percentage of components of the film materials if there is no chemical reaction.

The specified technical result is achieved by the fact that in the known method, a set of magnetron discharge current forces, the areas of the erosion zones of the targets and the densities of the target materials are specified, which ensure the formation of stoichiometric multicomponent film coatings. It is known that the spraying rate of materials is added by the expression [3]:

where j _u is the ion current density;

S _p - the atomization coefficient of the material;

N _a is the Avogadro number;

M _a is the atomic mass of the target material;

e is the electron charge;

ρ is the density of the target material.

It is known that the ion current density is determined by the expression:

where I is the magnetron discharge current;

S is the area of the target erosion zone;

The spray coefficient S _p can be determined from the expression [3]:

where M _u is the atomic mass of gas ions;

E _u is the energy of the incident ions;

E _c is the sublimation energy of the target atoms;

α is a dimensionless parameter depending on M _a / M _u .

If different chemical elements are included in the formula of the film material with different stoichiometric coefficients, then they must have different evaporation rates V _i , that is, be in the mixing zone and near the substrate with different concentrations so that

where V ₀ is a certain minimum evaporation rate;

and _i is the stoichiometric coefficient of the i-th member of the chemical

formulas A _a1 B _a2 ... D _ai

then the ratio of speeds can be written:

taking into account (1), (2) and (3), relation (5) can be represented as follows:

From expression (6), we can obtain the ratio for the magnetron discharge current strengths, the areas of the erosion zones of the targets, and the target densities, taking into account the parameters and stoichiometric coefficients of the film material:

Expression (7) shows the ratio of the magnitudes of the magnetron discharge currents, the area of the erosion zones of the targets and the density of the targets so that they contribute to the film according to the stoichiometric coefficients of its chemical formula or the percentage of components in the case of a mechanical mixture.

Thus, the method of forming a multicomponent stoichiometric film coating consists in setting a set of structural and technological parameters: magnetron discharge current strengths, areas of target erosion zones and target densities depending on the material properties and stoichiometric coefficients of the chemical formula or the percentage of components of the film materials if the chemical reaction absent, in accordance with formula (7).

A comparative analysis of the features set forth in the proposed technical solution with the features of the prototype shows that the inventive method for forming a multicomponent stoichiometric film coating differs from the prototype in that they specify a set of magnetron discharge currents, areas of target erosion zones and target densities depending on the properties of materials and composition films, in accordance with (7). All this indicates that the technical solution meets the criterion of "novelty."

Comparison of the claimed technical solution with other technical solutions in the given field of technology showed that the method of forming a multicomponent stoichiometric film coating, when a set of magnetron discharge current strengths, areas of target erosion zones and target densities are set depending on material properties and film composition, in accordance with ( 7) is unknown. In addition, the combination of essential features, together with the restrictive one, allows one to detect other properties of the claimed solution, in contrast to the known properties, which may include the following:

- providing stoichiometric or percent composition of the films by properly setting the sputtering speeds of the targets;

- providing a range of target sputtering rates by varying the magnetron discharge currents, areas of target erosion zones and target densities;

- the possibility of optimal selection of the areas of target erosion zones both by varying the strengths of the magnetron discharge currents and by varying the densities of the targets, or by simultaneously varying these parameters;

Thus, other, in contrast to the known properties inherent in the proposed technical solution, prove the presence of significant differences aimed at achieving a technical result.

The industrial applicability of the proposed technical solution is clearly demonstrated by the examples below.

Example 1. Figure 1 illustrates a method for forming a film coating of Bi ₂ Sr ₂ CaCu ₂ O ₈ (high temperature superconductor).

по (7). Необходимая информация приведена в таблице 1.The method by which the Bi ₂ Sr ₂ CaCu ₂ O ₈ film coating is formed is that four magnetrons with targets 1 (the fourth magnetron is not shown conventionally) made of Bi, Sr, Ca and Cu are placed in volumes 2, connected to the vacuum chamber 3, opposite each other. A pipe 4 is used to connect the vacuum chamber to the pumping system. The axes of the magnetrons 5 form a solid angle of 160 °, the apex of which faces the substrate 6 and is placed in a plane orthogonal to the substrate at a distance greater than the distance between opposite targets, and the device for attaching the substrate 7 made with the possibility of movement relative to the plane in which the vertex of the solid angle is located. In the area of sputtering of the targets, argon gas is supplied through the leakages 8, and pure oxygen is supplied to the film deposition region through the leakage 9. Opposite magnetron targets are sprayed into the mixing zone 10, while the direction of each of the opposing streams of atomized materials toward the substrate is rejected with the possibility of the formation of the resulting stream of atomized material from the mixing zone onto the substrate, which is moved relative to the resulting stream. The equipment used provided a range of changes in the area of target erosion zones from 5 to 25 cm ² , and adjustment of magnetron discharge currents from 0.3 to 2.0 A (values found experimentally). To set the set of structural and technological parameters of the process of forming a film coating of Bi ₂ Sr ₂ CaCu ₂ O ₈ , calculations of the corresponding concepts were performed

by (7). The necessary information is given in table 1.

Table 1 No. Material a M _a (g / mol) E _c (eV) ρ ₀ (g / cm ³ ) M _u (g / mol) α one Cu 2 63.5 3,5 8.96 0.40 2 Sr 2 87.6 2.7 2.63 39.95 (Ar) 0.45 3 Ca one 40.1 3.0 1,54 0.30 four Bi 2 209.0 3,7 9.80 0.80

ρ ₀ is the density of the compact target material (monolithic).

Substituting the data from table 1 in (7), we obtained the relation

Since Ca has the lowest density of a compact material, we will consider the magnetron with a target of this material to be basic, that is, we will assume that the density of the Ca target and the area of its erosion zone are already set. The values of k are presented in Table 2. Since Sr has a density of compact material and coefficient k close to Ca, we set the area of the erosion zone of its target to be the same as that of Ca (we can use a magnetron similar to the base one), and the density of its target is equal to density of compact material Sr. Bi and Cu have densities of compact materials significantly higher than the base density of compact Ca material, but differ slightly from each other; therefore, to approximate the sputtering processes of the materials of the corresponding targets to the sputtering processes of Ca and Sr targets, we set their densities to 0.6ρ ₀ (the least experimentally determined densities of powder compacts for these materials, at which they do not crumble and can be mounted on magnetrons as targets), which will be ensured by pressing Bi and Cu powders with taking into account the expression [4]:

where ρ _CR - the density of the pressed material;

ρ _us is the density of the poured powder;

P is the pressing pressure;

b is a constant depending on the properties of the powder.

Since the coefficient k of the Bi material is much larger than that of Cu, it compensates for the gap between the sputtering processes of the base target and the Bi target enough to use a magnetron with the same target erosion area as Ca, while the value of the coefficient k of the material Cu is insufficient for such compensation and requires the use of a magnetron with a smaller area of the erosion zone of the target. Finally, the formation of the mixing zone of the sprayed materials Cu, Sr, Ca and Bi and their concentration in the film in accordance with their stoichiometric coefficients of the chemical formula Bi ₂ Sr ₂ CaCu ₂ O _{8 is} carried out by setting the discharge currents of the corresponding magnetrons, taking the base current of the base magnetron with target from Ca. The calculation results are presented in Table 2. After the calculation, Cu and Bi targets were formed by unilaterally pressing the powders of these materials into molds using a hydraulic press. The pressing pressure was 30 ... 40 MPa. Targets from Ca and Sr were made in the usual mechanical way. For sputtering, magnetrons with areas of target erosion zones were used according to the calculated values (see table 2). After manufacturing, the targets were mounted on the corresponding magnetrons and sprayed, adjusting the strength of the discharge currents of the respective magnetrons according to the calculated values (see table 2).

table 2 No. Material k S (cm ² ) ρ (g / cm ³ ) I (A) one Cu 0.86 10.0 5.38 (0.6ρ ₀ ) 2.0 2 Sr 1,57 20,0 2.63 (ρ ₀ ) 1,1 3 Ca 1.00 20,0 1.54 (ρ ₀ ) 1,0 four Bi 3.04 20,0 5.88 (0.6 / ρ ₀ ) 1.3

Thus, as a result of setting the areas of magnetron target erosion zones, target densities, and magnetron discharge currents in accordance with Table 2 in the mixing zone and near the substrate, the sprayed materials were found with stoichiometric coefficients corresponding to their content in the chemical formula Bi ₂ Sr ₂ CaCu ₂ O ₈ . As a result of the supply of oxygen to the substrate zone and its reactive interaction with atomized materials in stoichiometric proportions near the substrate, a Bi ₂ Sr ₂ CaCu ₂ O ₈ film was formed on it. Measurements showed satisfactory compliance of the material composition of the resulting coating with the chemical formula.

Example 2. Figure 2 illustrates a method for forming a film coating of a mechanical mixture (solid solution) of 70% Ag 30% Au.

по формуле (7). Необходимая информация приведена в таблице 3.The method by which a film coating of 70% Ag 30% Au is formed is that two magnetrons with targets 1 made of Ag and Au are placed in volumes 2 connected to the vacuum chamber 3, opposite each other. A pipe 4 is used to connect the vacuum chamber to the pumping system. The axes of the magnetrons 5 form a solid angle of 160 °, the apex of which faces the substrate 6 and is placed in a plane orthogonal to the substrate at a distance greater than the distance between opposite targets, and the device for attaching the substrate 7 made with the possibility of movement relative to the plane in which the vertex of the solid angle is located. In the field of sputtering targets through leaking 8 feed argon gas. Opposite magnetron targets are sprayed into the mixing zone 9, while the direction of each of the opposing streams of atomized materials toward the substrate is rejected with the possibility of the formation of the resulting stream of atomized material from the mixing zone onto the substrate, which is moved relative to the resulting stream. The equipment used provides a range of changes in the area of target erosion zones from 5 to 25 cm ² , and adjustment of magnetron discharge currents from 0.3 to 2.0 A (values found experimentally). To set the set of structural and technological parameters of the process of forming a film coating of 70% Ag 30% Au, the corresponding concepts were calculated

by the formula (7). The necessary information is given in table 3.

Table 3 No. Material A (%) M _a (g / mol) E _c (eV) ρ ₀ (g / cm ³ ) M _u (g / mol) α one Ag 70 107.8 2.7 10.5 0.58 39.95 (Ar) 2 Au thirty 197 3.92 19.32 1,0

ρ ₀ is the density of the compact target material (monolithic). Substituting the data from table 3 in the formula (7) received the ratio (8). Since Ag has the lowest density of a compact material, we will consider the magnetron with a target of this material to be basic, that is, we will assume that the density of the target from Ag and the area of its erosion zone are already given. The values of k are presented in Table 4. It can be seen from Table 3 that Au has a density of compact material higher than that of Ag, however, the coefficient k of the Au material is also significantly larger than that of Ag, which compensates for the gap between the sputtering processes of the base target and the target from Au it is enough to use a magnetron with the same area of the target erosion zone as that of the base target, and to make the target from Au of the same density as the density of a compact (monolithic) Au material. Thus, in this case, the formation of the mixing zone of atomized Ag and Au materials and their concentration in the film in accordance with their specified percentage is carried out by setting the discharge currents of the corresponding magnetrons, taking the base current of the base magnetron with the Ag target as the base current. The calculation results are presented in table 4. After the calculation, the targets are made of Ag and Au in the usual mechanical way. For sputtering, magnetrons are used with areas of the target erosion zones according to the given values (see Table 4). After manufacturing, the targets are mounted on the corresponding magnetrons and sprayed, adjusting the strength of the discharge currents of the respective magnetrons according to the calculated values (see table 4).

Table 4 No. Material k S (cm ² ) ρ (g / cm ³ ) I (A) one Ag 1,0 10.0 10.5 (ρ ₀ ) 1,0 2 Au 3.6 10.0 19.32 (ρ ₀ ) 0.5

Thus, as a result of setting the areas of magnetron target erosion zones, target densities and magnetron discharge currents in accordance with Table 4 in the mixing zone and near the substrate, the sprayed materials are in a percentage ratio corresponding to their specified values, forming a film coating of 70% Ag 30% Au on the substrate.

Using the proposed method of forming a multicomponent stoichiometric film coating can improve the quality of the coating, its stoichiometry or composition.

Information sources

1. Golovashkin A.I. Methods for producing films and coatings from high-temperature superconductors // Journal of the All-Union Chemical Society named after D.I. Mendeleev.- M.: “Chemistry”, 1989, v. 34, No. 4.- p. 481-492.

2. Patent RU 2211881 C2, 09/10/2003.

3. Nikonenko V.A. Mathematical modeling of technological processes. Workshop / Ed. G.R. Kuznetsova. - M.: MISiS, 2001 .-- 48 p.

4. Okizaki K. Technology of ceramic dielectrics. Per. from japanese. M.: Energy, 1976. - S.58-64.

Claims (1)

A method of forming a multicomponent stoichiometric film coating, including magnetron sputtering of opposing targets, directing the sprayed material into the mixing zone formed by at least two opposing streams of sprayed material, deviating the direction of each of the opposing streams of sprayed material toward the substrate with the possibility of forming a resulting stream of sprayed material from the mixing zone to the substrate, the movement of the substrate relative to the resulting stream, precipitated sputtering the material onto the substrate, characterized in that a set of structural and technological parameters is set: the magnetron discharge currents, the areas of the erosion zones of the targets and the target densities, the relationship between which is determined by the properties of the materials and stoichiometric coefficients or the percentage of components of the film material in the ratio

where ρ _i is the density of the target material of the i-th element; I _i is the discharge current strength of the i-th magnetron; S _i - the area of the erosion zone of the i-th target; and _i is the stoichiometric coefficient of the i-th element in the chemical formula or the percentage of the i-th element in the film; M _ai is the atomic mass of the target material of the i-th element; M _u is the atomic mass of gas ions; E _ci is the sublimation energy of the target atoms of the i-th element; α _i is the dimensionless parameter of the target material of the i-th element, depending on M _a / M _u ; ρ ₁ is the density of the target material of the base element having the lowest density of the compact material; S ₁ - the area of the erosion zone of the target of the base element having the lowest density of compact material; and ₁ is the stoichiometric coefficient of the base element having the lowest density of the compact material, chemical formula, or the percentage of the base element having the lowest density of the compact material in the film; M _a1 is the atomic mass of the target material of the base element having the lowest density of the compact material; E _c1 is the sublimation energy of the target atoms of the base element having the lowest density of the compact material; α ₁ is the dimensionless parameter of the target material of the base element having the lowest density of the compact material, depending on M _a / M _u .

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